The Air view is pretty consistent for me, but the air gestures were not worth looking like a fool waving at my phone to get something to work so I disabled it.
I figured it out. For example airview... Settings / Motions and gestures. make sure it's on then to the left of on tap to open set to auto.
for Air gestures make sure you do the same and your hand must float over the sensor at the top of the phone just under the samsung name.
Jim
after upgrade to KITKAT, I found my air gesture is disable each time I clear my ROM.......I have to manually enable it every time I clear ROM. Anyone encounter same issue??? please help